I believe the requirement is supposed to be a valid home country M/C licence (or endorsed International one) to hire any motorcycle, it is simply hardly enforced and difficult for the locals to verify, so they don't bother. The renting out of larger bikes, over say 200cc, should be a more specialist supply. A 125 cc scooter, for tourists to whiz to the beach and around the island, should be more than ample. Giving some kid a 600cc crotch rocket is simply madness.